A chlorosulfonated polymer typified by chlorosulfonated polyethylene has properties similar to those of chloroprene rubber.
However, since the chlorosulfonated polymer is excellent in heat resistance, weather resistance and ozone resistance as compared with chloroprene rubber, the chlorosulfonated polymer is frequently used as a polymer having more excellent heat resistance.
Accordingly, in the field wherein the heat resistance of conventional chloroprene rubber is yet insufficient, it has been attempted to replace the chloroprene rubber with a chlorosulfonated polymer.
For example, there are rubber belts such as toothed belts and poly-V-belts made of such a chlorosulfonated polymer.
However, since chlorosulfonated polyethylene is inferior in cold resistance as compared with chloroprene rubber, it is sometimes difficult to clear the problem of the cold resistance required for toothed belt.
On the other hand, in the field of toothed rubber belt, it is the most important technical theme to improve the water resistance of the product in addition to the aforesaid heat resistance and cold resistance thereof.
It is known that for improving the heat resistance and water resistance of the vulcanized product of chlorosulfonated polyethylene, the use of a lead compound such as litharge, red lead oxide, etc., as an acid-acceptor is effective. However, the use of such a lead compound is undesirable because of the problem of environmental pollution by toxicity of the lead compound.